gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Inset Text on Top Layer Full of Voids

Wed Mar 11, 2020 10:58 pm

I'm trying to print some text on the top of a small model. No matter what I've tried, I get holes in the top most layer or two (the text is two layers deep). I've tried all sorts of combinations of settings for internal & external single extrusions, different temperatures, speeds, cooling etc. The preview shows that material SHOULD be deposited in lots of places where it is absent. I can't tell if it's a bug and it's not actually trying to put down material where the voids are, or it they are so small that they aren't sticking to the previous layer.

I'm using eSun PLA+, which has always worked well for me in the past. This spool seems to be a bit different. For example, I had to change from glue stick on glass to Kapton to get good adhesion. I even tried drying the filament for several days, but it didn't make any difference.

Here's what the preview looks like, and I've circled a bunch of places where I get voids in the print:
Top Layer Voids.jpg
And here's the best photo I could get showing what actually happens:
Top Layer Voids on Print.jpg
As an example, the top & bottom loops of the S's should be filled, but there's nothing there.

I've also attached the factory file. There are two processes, one to get the bottom section right with a fixed bridging angle, and the 2nd process has automatic bridging angle and the settings for the top text.
Tri-Blade Screwdriver.factory
(90.3 KiB) Downloaded 27 times
Any ideas or suggestions would be greatly appreciated. I need to make 50 of these, and I really want to get them looking a lot better than they are now.

Thanks!

User avatar
dkightley
Posts: 2167
Joined: Tue Mar 10, 2015 4:09 pm

Re: Inset Text on Top Layer Full of Voids

Thu Mar 12, 2020 6:03 am

Try the attached...

I've added a third profile where I've dropped the outlines for the top two layers down to 1. And I've upped the outline overlap from 20% to 70%.


EDIT... You could try doing the same for the first three layers to improve the text on the bottom
Attachments
Tri-Blade Screwdriver.factory
(94.63 KiB) Downloaded 24 times
Doug Kightley
Volunteer at the National Tramway Museum http://www.tramway.co.uk
Railway modeller and webmaster at http://www.talkingtgauge.net

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Thu Mar 12, 2020 8:18 am

Thanks! As I was nodding off last night, it occurred to me that I may be barking up the wrong settings tab. I had to adjust the retraction settings, and I bet the Extra Restart Distance is off. That would explain the disappearance of the small features.

I'll try your fix & also see if more ERD helps. All the previous filament spools of this stuff needed a negative ERD, but this may need to be positive. This spool is definitely different.

We'll see...

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Thu Mar 12, 2020 1:48 pm

Well, raising the ERD helped a little, and going to a single perimeter on the top also helped, but it's still leaving out major chunks all over the place:
Single Perim Voids.jpg
I'm running out of ideas... The rest of the print look pretty normal, and the voids are very repeatable, so I don't think it's an issue with bad spots in the filament, loose wires, etc.

User avatar
dkightley
Posts: 2167
Joined: Tue Mar 10, 2015 4:09 pm

Re: Inset Text on Top Layer Full of Voids

Thu Mar 12, 2020 7:22 pm

Looking at your photo and the profiles, I can make a few suggestions, as you should get really good results with PLA. Instead, you're getting what looks like the filament being extruded really hot and the extruder is ripping the molten plastic away before it cools down and solidifies in place.

1) Slow down the X/Y movement speed. You have it running at lightning speed & I'm sure its ripping the freshly laid filament out.
2) Cooling fan at zero for first layer only....then on max for every line to end of print. PLA needs cooling quickly except for 1st layer, where you want it to be softer.
3) Don't hot up the filament for the top layers...leave at 215.
4) I'd also look at your retraction & coast settings. It looks like with no coast, you may be getting a slight excess of material that you're trying to compensate for with negative extra restart.. Again, I think the fast XY movement is ripping the just laid plastic out!
Doug Kightley
Volunteer at the National Tramway Museum http://www.tramway.co.uk
Railway modeller and webmaster at http://www.talkingtgauge.net

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Thu Mar 12, 2020 8:50 pm

I was thinking along the same lines several days ago, and tried a three layer setup with the top section running at half speed. It didn't help, but that was several changes ago, so I'll try it again.

Thanks!

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Sat Mar 14, 2020 2:38 pm

Well, I tried 100% cooling on the top section, with the temperature at 215, and half speed. No noticeable improvement.

I found an old factory file from when I was developing the prototype for this, and tried running that. It's a single profile, and although it's not perfect, it does a LOT better on the top text than anything I've tried in the last week. I'm going over it carefully to see what the secret is. By breaking the printing into three levels, I have been able to optimize some other aspects, and I want incorporate those improvements as well.

I'll post an update once I have pinned down the differences between the old process that works so much better than the current one.

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Sun Mar 15, 2020 9:44 pm

I've gone through the old prototype settings that are working MUCH better than my recent efforts, and I put the differences into a spreadsheet:
PLA+ Screwdriver Profiles.pdf
(68.69 KiB) Downloaded 27 times
The old settings were a single profile for the enter model, and there are several places where there are differences that shouldn't affect the top layer print.

The most likely differences are:

Retraction settings: more retraction, 0 restart distance and retracting between layers works better
Temperature: Top layers at 210C instead of 220C works better
Cooling: 60% on top layers is better than 0

The biggest difference is in the thin wall settings. I could swear I tried the combination of Perimeters Only & Gap fill early on, and found that single extrusion walls & fill worked better, but maybe not.

I'm starting by running the print with the modified retraction settings, and will add in the other changes one by one to see what is making the difference.

gwhite
Posts: 119
Joined: Wed Jul 19, 2017 9:37 am

Re: Inset Text on Top Layer Full of Voids

Thu Mar 26, 2020 7:03 pm

Well, after several days of trying all sorts of things, I finally came up with a combination that worked. From the original file, the only settings i had to change were:

Under the Extruder settings:
RetractionDistance: from 0.6 to 0.7
ExtraRestartDistance: from -0.2 to +0.07

Under Infill:
OutlineOverlapPercentage: from 10 to 15
ExternalInfillAngles: from -45, 45 to -30, 45 (This aligned the fill better with the text, especially the loops in the 'S's)

Under Advanced
SingleExtrusionMaxPrintingWidthPercentage: from 200 to 150
SingleExtrusionEndpointExtension: from 0.2 to 0.6

The biggest impact was changing the Extra Restart Distance. Increasing the Single Extrusion Endpoint Extension filled in the last few small holes.

It now looks like (sorry for the poor contrast photo):
No Top Layer Voids.jpg
It was very important to use multiple processes. Using the same ERD on lower parts of the model produced horrible zits & ridges.

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